The certification of what is believed to be the largest class ever in a privacy lawsuit was upheld when the 7th U.S. Circuit Court of Appeals declined to accept an appeal of the lower court’s certification order.

Two consumers brought suit against comScore, alleging that after they downloaded a free product, the company improperly obtained and used personal information from their computers in violation of the Stored Communications Act, the Electronic Communications Privacy Act, and the Computer Fraud and Abuse Act. Despite a license agreement that notifies consumers that information will be collected for market research, the plaintiffs claimed comScore exceeded the scope of consumers’ consent by collecting information like phone numbers, user names, passwords, credit card numbers, and other demographic information.

In April a federal court judge in Illinois certified a class of all consumers who had downloaded comScore’s software since 2005, estimated at up to 10 million individuals. At the time, class counsel called it “the largest privacy case ever certified on an adversarial basis.”

The court declined to accept comScore’s argument that certification was inappropriate because the scope of consent will vary for each plaintiff that various statute of limitations are applicable for different plaintiffs, and that individual assessments will be necessary for each class member’s damages.

comScore appealed the certification order to the 7th Circuit with the support of amici like the Direct Marketing Association, the American Association of Advertising Agencies, the Association of National Advertisers, the Entertainment Software Association, the Interactive Advertising Bureau, and the Chamber of Commerce.

The groups told the court they were “gravely concern[ed]” about the “remarkable certification order,” which implicates “foundational Internet communication and industry best-practices disclosures” as challenged in the case.

The groups explained that the suit against comScore is representative of a “groundswell of privacy class actions” against members of the groups, they explained, which are brought “under ill-fitting statutes by uninjured named plaintiffs presenting uncorroborated (and often testable) allegations.” Analogizing comScore to the Nielsen Company’s ratings system for television – and emphasizing the fact that consumers assented to the collection of their information by consenting to the license agreement – the groups “are justifiably alarmed by the ease with which these plaintiffs were allowed to suspend disbelief and obtain certification of a class challenging disclosures that plainly advise [consumers] that comScore’s system will comprehensively monitor all activity and configurations on the computer to which it is downloaded.”

Based on the importance and the novelty of the issues involved in the case, the amici requested the 7th Circuit review the certification order. With such a large class, comScore could be pushed into a “blackmail settlement,” the motion cautioned, suffer reputational harm, chill voluntary participation in market research, and adversely impact members of the amici groups that rely on Web rating services.

However, the federal appellate court declined to grant comScore’s appeal, effectively upholding the class certification and moving the case one step closer to trial.

To read the district court’s ruling certifying the class in Harris v. comScore, click here.

To read the amicus brief filed by the industry groups on behalf of comScore, click here.

Why it matters: The 7th Circuit’s decision not to review the class certification order pushes the case against comScore forward even closer to trial. However, as the industry amici noted in their briefs, the defendant may seek to settle the case rather than face a multi-million member class. “Most class actions settle after certification because the risks of trying thousands of claims in a single lawsuit often are too great for rational corporate decision-makers to bear,” the groups wrote.